Haematology Overview and Blood Cell Disorders

Haematology is the study of blood and blood disorders.
Learning objectives include relating pathophysiology and etiology of hematological disorders, describing epidemiology, manifestations, and management.
Skills include interpreting clinical manifestations and investigations of hematological disorders to formulate reasonable diagnoses, applying evidence-based management plans for such disorders, and distinguishing patients in emergencies for comprehensive management plans ensuring normal homeostasis.

Includes discussion of red blood cell development starting from the yolk sac in the third week of intrauterine life, and later, the liver and spleen contributing by the third month.
Bone Marrow (BM) starts contributing from the fourth month in the womb.
In adult life, red blood cell production is restricted to the ends of long bones (like the head of the femur) and flat bones (like the skull, sternum, and ribs).
Stages of development progress from totipotent stem cells to pluripotent stem cells, to committed stem cells for erythropoiesis, proerythroblasts, erythroblasts, normoblasts, and reticulocytes (containing residual RNA).
Development ultimately leads to red blood cells (RBCs).

**RBC Shape:**Normal RBCs are biconcave. Abnormal shapes include spherocytes, sickle cells, and target cells.
RBC Count: Normal ranges vary by sex (males 4.5-6 million/mm3, females 3.8-4.8 million/mm3). Abnormal values indicate anemia (low count) or polycythemia (high count).
RBC Diameter: Normal diameter is 7.2 microns. Abnormal values indicate microcytes (small), macrocytes (large), megalocytes (very large), or anisocytosis (variable size).
Hematocrit (PCV): Percentage of packed RBCs in 100ml of blood. Normal is 45%. Increased PCV indicates dehydration or polycythemia; decreased PCV suggests hypervolemia or anemia.
Mean Corpuscular Volume (MCV): Average volume of RBCs. Values above 100 fL indicate macrocytic cells; values below 78 fL indicate microcytic cells.
Mean Corpuscular Hemoglobin (MCH): Average amount of hemoglobin per RBC. Abnormal values indicate possible problems.
Mean Corpuscular Hemoglobin Concentration (MCHC): Average concentration of hemoglobin per RBC volume. Abnormal values can suggest specific conditions.
Hemoglobin (Hb): Grams of hemoglobin per deciliter of blood. Normal levels vary by sex (males 13.5-16 gm%, females 11.5-13.5 gm%).
Erythrocyte Sedimentation Rate (ESR): Rate at which RBCs settle in a blood sample. Measures inflammation. Normal values differ by sex.

Reticulocytes are immature red blood cells.
Their count is an indicator of bone marrow activity.
Increased reticulocyte counts indicate increased RBC production in response to hemolysis, acute hemorrhage, or treatment of anemia.
Reduced counts indicate bone marrow failure.
Normal counts range from 0.2-2% of RBCs.

Defined as a reduced oxygen-carrying capacity of blood, typically identified by Hb < 11.5 gm% in females or Hb < 13 gm% in males.
Etiology includes diminished intake, diminished absorption, increased loss, and increased requirements.
Clinical picture includes pallor, dizziness, tinnitus, lack of concentration, tingling, numbness, tachycardia, palpitations, and functional murmurs.

Classified by etiology or type (normocytic normochromic, microcytic hypochromic, macrocytic normochromic).
Specific types of microcytic hypochromic anemia include iron deficiency anemia, thalassemia, sideroblastic anemia, and anemia of chronic illnesses.
Megaloblastic anemia (a type of macrocytic normochromic anemia) has causes like folic acid deficiency and vitamin B12 deficiency.
Hemolytic anemia is categorized by corpuscular (cell) and extracorpuscular defects, affecting the cell's lifespan abnormally.

Physiological overview: shortened RBC lifespan, bone marrow compensating for production, hemolysis occurring in the reticuloendothelial system (RES) or intravascularly.
Etiology: defects in cellular components and extra-cellular causes.
Hemolytic anemia symptoms can include jaundice, pallor, fatigue, and increased spleen size.

Investigations are essential for determining blood cell type or if the blood has specific abnormal characteristics.
Tests like hemoglobin, hematocrit, complete blood count, and others are important.

Hemostasis is the process that keeps blood within blood vessels and prevents bleeding.
Hemostasis involves a delicate balance between clotting and anti-clotting systems.
It also includes factors from blood vessels, platelets, and coagulation factors to maintain blood flow within vessels.

Total WBC count ranges from 4000-11000 mm³.
Includes neutrophils, basophils, eosinophils, monocytes, and lymphocytes, each with ranges of percentages.
Immature WBCs are 5-10% of total WBCs.

Leukemia involves abnormal, uncontrolled proliferation of leucopoietic cells, and discharge of abnormal leukocytes.
Types include acute and chronic leukemias; additionally, they're classified by myeloid or lymphoid origins.
Etiological factors can include radiation, chemicals, drugs, genetic factors, and infections/viruses.